Effect of Star-shaped Chain Architectures on the Polylactide Stereocomplex Crystallization Behaviors

Linear and star-shaped polylactides（PLA） with similar molecular weights of each arm are synthesized via ringopening polymerization of LA with 3-butyn-1-ol and pentaerythritol as initiators,respectively.By solution blending of equivalent mass of poly（L-lactic acid）s（PLLAs） and poly（D-lactic acid）s（PDLAs）,perfect PLA stereocomplexes（sc PLAs） are prepared and confirmed by WAXD and FTIR analysis.Effect of chain architectures on stereocomplex crystallization is investigated by studying the non-isothermal and isothermal crystallization of linear and star-shaped polylactide stereocomplexes.In dynamic DSC and POM test,star-shaped PLLA（4s PLLA）/PDLA and PLLA/star-shaped PDLA（4s PDLA） stereocomplexes reach rapid crystallization and higher crystallinity due to larger spherulite density of star-shaped chain and excellent chain mobility of linear chain.In isothermal crystallization test,much faster crystallization and less crystallization half-time is obtained with the increase of star-shaped chain.Meanwhile,4s PLLA/PDLA and PLLA/4s PDLA are found to have the highest crystallinity,suggesting limitation of too much star-shaped chain for 4s PLLA/4s PDLA and restriction of linear chain in nucleation capacity for PLLA/PDLA.The results reveal that star-shaped chain has an important influence on the crystallization of sc PLAs.